Yeah, that works. Make sure you really like Windows 8 before you upgrade and make an image of your Windows 7 system so that you can go back in case you do not like it . Many people have reservations about Windows 8.

The best thing is to first try it out in virtual. Here is how. That's the way I run it. Works great. And with the VMware tools, you have a shared clipboard with which you can move files back and forth.

Homegroup sharing between Win7 and Win8 works well. All you need is the group password, identical to sharing between groups of Win7 computers. I doubt that the existing password will persist on the upgraded PC after the upgrade, but if you got it to work in Windows 7 it is easy to get it to work across a 7 & 8 homegroup.